WordPress Virtual Page - "Trying to obtain property 'post_type' of non-object"

Question

I'm building a WordPress plugin that uses dummy pages to display data fetched from an API.

The setup is relatively simple. I have a rewrite rule for the URLs that the plugin wants to work on, and when I hit specific query_vars I launch a dummy page.

public function __construct()
{

    require_once plugin_dir_path(__FILE__).'vendor/autoload.php';

    add_action('init', [$this, 'rewrite_rule'], 1);

    // add query vars
    add_action('query_vars', [$this, 'add_query_vars_filter'], 1);

    // virtual page init
    add_filter('the_posts', [$this, 'virtual_page'], 1);

}
public function virtual_page($posts)
{

    global $wp, $wp_query;

    if (!empty(get_query_var('plugin'))) {
        $plugin = get_query_var('plugin');
    }

    if (!empty($plugin)) {

        $post = new stdClass();
        $post->post_author = 1;
        $post->post_name = 'lorem ipsum';
        $post->guid = get_bloginfo('wpurl').'/';

        $post->post_title = 'title';
        $post->post_content = 'content';

        $post->ID = -999;
        $post->post_type = 'page';
        $post->post_status = 'static';
        $post->comment_status = 'closed';
        $post->ping_status = 'open';
        $post->comment_count = 0;
        $post->post_date = current_time('mysql');
        $post->post_date_gmt = current_time('mysql', 1);
        $posts = NULL;
        $posts[] = $post;

        $wp_query->is_page = true;
        $wp_query->is_single = false;

        $wp_query->is_singular = true;
        $wp_query->is_home = false;
        $wp_query->is_archive = false;
        $wp_query->is_category = false;

        unset($wp_query->query["error"]);
        $wp_query->query_vars["error"] = "";
        $wp_query->is_404 = false;

        remove_filter('the_content', 'wpautop');
        remove_filter('the_excerpt', 'wpautop');

        return $posts;
    }
}

This code does what is expected, which is to display a dummy page with the content I need, but I get a warning in PHP 8.0:

"Attempt to read property "post_type" on null"

I believe the order of execution here is wrong because I'm getting empty $post and $wp_query in xdebug. My guess is that the virtual page function is executed too early.

I tried debugging this issue for a long time but unfortunately I lacked backend/WordPress knowledge.

If anyone can help, I would be more grateful.

Answer 1

If you try to use virtual pages in WP 6.1, you will no longer have a post ID. This line causes it to break.

$post->ID = -999;